The disclosure relates generally to distributed communications systems (DCS), such as distributed antenna systems (DAS) as an example, and more particularly to selective non-distribution of received unlicensed spectrum communications by a remote unit(s) into a DCS.
Wireless customers are increasingly demanding digital data services, such as streaming video signals. At the same time, some wireless customers use their wireless communication devices in areas that are poorly serviced by conventional cellular networks, such as inside certain buildings or areas where there is little cellular coverage. One response to the intersection of these two concerns has been the use of DASs. DASs include remote antenna units (RAUs) configured to receive and transmit communications signals to client devices within the antenna range of the RAUs. DASs can be particularly useful when deployed inside buildings or other indoor environments where the wireless communication devices may not otherwise be able to effectively receive RF signals from a source.
In this regard, FIG. 1 illustrates distribution of communications services to remote coverage areas 100(1)-100(N) of a DAS 102, wherein ‘N’ is the number of remote coverage areas. These communications services can include cellular services, wireless services, such as RF identification (RFID) tracking, Wireless Fidelity (Wi-Fi), local area network (LAN), and wireless LAN (WLAN), wireless solutions (Bluetooth, Wi-Fi Global Positioning System (GPS) signal-based, and others) for location-based services, and combinations thereof, as examples. The remote coverage areas 100(1)-100(N) are created by and centered on RAUs 104(1)-104(N) connected to a centralized equipment 106 (e.g., a head-end controller, a head-end unit, or a central unit). The centralized equipment 106 may be communicatively coupled to a source transceiver 108, such as for example, a base transceiver station (BTS) or a baseband unit (BBU). In this regard, the centralized equipment 106 receives downlink communications signals 1100 from the source transceiver 108 to be distributed to the RAUs 104(1)-104(N). The downlink communications signals 1100 can include data communications signals and/or communication signaling signals, as examples. The RAUs 104(1)-104(N) are configured to receive the downlink communications signals 110D from the centralized equipment 106 over a communications medium 112 to be distributed to the respective remote coverage areas 100(1)-100(N) of the RAUs 104(1)-104(N). In a non-limiting example, the communications medium 112 may be a wired communications medium, a wireless communications medium, or an optical fiber-based communications medium. Each of the RAUs 104(1)-104(N) may include an RF transmitter/receiver (not shown) and a respective antenna 114(1)-114(N) operably connected to the RF transmitter/receiver to wirelessly distribute the communications services to user equipment (UE) 116 within the respective remote coverage areas 100(1)-100(N). The RAUs 104(1)-104(N) are also configured to receive uplink communications signals 110U from the UEs 116 in the respective remote coverage areas 100(1)-100(N) to be distributed to the source transceiver 108.
The source transceiver 108 discussed above with regard to the DAS 102 in FIG. 1 is configured to transmit licensed spectrum. Licensed spectrum is spectrum (i.e., a signal frequency band) purchased by a carrier for exclusive use for communications services to avoid interference with other carrier communications signals. For example, cellular communications services are provided in licensed spectrum in licensed communications frequency bands between 700 MegaHertz (MHz-1900 MHz. Use of licensed spectrum also allows for communications services in licensed spectrum to be managed. For example, long term evolution (LTE) technology is a managed technology where each UE has to be identified by a LTE base station. The LTE base station controls time slots when the UE can transmit and receive communications signals. However, purchasing licensed spectrum is expensive. On the other hand, unlicensed spectrum is spectrum that is made available for use by any carrier or communication service equipment without licensing. Thus, unlicensed spectrum is advantageously supported by many devices and equipment with communications capabilities to avoid the need to purchase licensed spectrum. For example, 5 GHz is an unlicensed spectrum that is used in access points (APs) for WiFi communications as well as other communications devices, such as cordless phones. In this regard, carriers can advantageously provide BTSs or BBUs designed to transmit communications signals in unlicensed spectrum to take advantage of the additional bandwidth provided by the unlicensed spectrum. In this regard, as shown in FIG. 2A, the source transceiver 108 may be configured to transmit downlink communications signals 110D in an unlicensed communications frequency band. As shown in FIG. 2B, the source transceiver 108 may also be configured to transmit downlink communications signals 110D (e.g., data and signaling signals) in a licensed communications frequency band and other data communications signals in an unlicensed communications frequency band. However, use of unlicensed spectrum can cause mutual interference issues between a source transceiver and other transceivers both transmitting in the same unlicensed spectrum at the same time. Use of unlicensed spectrum can be even more problematic in DASs, such as the DAS 102 in FIG. 1, because the DAS expands the reach of the source transceiver to multiple remote coverage areas.
Because of the desire by communications service providers to use unlicensed spectrum to gain additional bandwidth without additional licensing costs, mechanisms have been designed and implemented to avoid or reduce interference issues with use of unlicensed spectrum. One such mechanism is “Listen Before Talk (LBT).” LBT is a mechanism proposed by the 3rd Generation Partnership Project (3GPP) for minimizing interferences between two transceivers operating in the same unlicensed channel(s). In this regard, a transceiver can start signal transmission of a communications signal in an unlicensed channel after verifying that the unlicensed channel is free for use, meaning that another transceiver is not presently transmitting signals in the same unlicensed channel. Before transmission, the transceiver first listens to the activity “on the air” i.e., on the unlicensed channel where it intends to transmit), or verifies that the unlicensed channel is not occupied by another transmission. If a transmission in the same unlicensed channel is detected, the transmitter postpones its intended transmission until the unlicensed channel is free. When two transceivers coordinate their activity through use of LBT, each transceiver will have a certain likelihood of finding transmission opportunities where an unlicensed channel is free for transmission signals. However, when a source transceiver, such as a BTS or BBU for example, coupled to a DAS transmits communications signals in unlicensed channels to the DAS for distribution, the source transceiver will have to coordinate its activity with all unlicensed transceivers transmitting signals to the remote units in the DAS (i.e., “seen” by the DAS). This can force the source transceiver to remain silent for long periods, thus significantly lowering the throughput of the communications services supported by the DAS. Even one remote unit distributing unlicensed communications signals in a DAS may be enough to cause a source transceiver to be silent in unlicensed channels for long periods of time.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.